Peroxycarboxylic acid compositions can be effective antimicrobial agents. Methods of using peroxycarboxylic acids to clean, disinfect, and/or sanitize hard surfaces, textiles, meat products, living plant tissues, and medical devices against undesirable microbial growth have been described (U.S. Pat. No. 6,545,047; U.S. Pat. No. 6,183,807; U.S. Pat. No. 6,518,307; U.S. Patent Application Publication No. 2003-0026846; and U.S. Pat. No. 5,683,724). Peroxycarboxylic acids have also been used in a various bleaching applications including, but not limited to, wood pulp bleaching/delignification and laundry care applications (European Patent 1040222B1; U.S. Pat. No. 5,552,018; U.S. Pat. No. 3,974,082; U.S. Pat. No. 5,296,161; and U.S. Pat. No. 5,364,554). The desired efficacious concentration of peroxycarboxylic acid may vary according to the product application (for example, ca. 500 ppm to 1000 ppm for medical instrument disinfection, ca. 30 ppm to 80 ppm for laundry bleaching or disinfection applications) in 1 min to 5 min reaction time at neutral pH.
Enzymes structurally classified as members of family 7 of the carbohydrate esterases (CE-7) have been employed as perhydrolases to catalyze the reaction of hydrogen peroxide (or alternative peroxide reagent) with alkyl esters of carboxylic acids in water at a basic to acidic pH range (from ca. pH 10 to ca. pH 5) to produce an efficacious concentration of a peroxycarboxylic acid for such applications as disinfection (such as medical instruments, hard surfaces, textiles), bleaching (such as wood pulp or paper pulp processing/delignification, textile bleaching and laundry care applications), and other laundry care applications such as destaining, deodorizing, and sanitization (Published U.S. Patent Application Nos. 2008/0176783, 2008/0176299, 2009/0005590, and 2010/0041752 to DiCosimo et al.). The CE-7 enzymes have been found to have high specific activity for perhydrolysis of esters, particularly acetyl esters of alcohols, diols and glycerols. However, CE-7 perhydrolases may also hydrolyze the carboxylic acid ester substrate. As such, it is often preferable to employ an enzyme catalyst having high selectivity for perhydrolysis (P) relative to hydrolysis (H) when synthesizing peroxycarboxylic acids from carboxylic acid esters (i.e., an enzyme catalyst having a higher “P to H” ratio). Published U.S. Patent Application No. 2010/0087529 to DiCosimo et al. describes several variant CE-7 perhydrolases derived from several Thermotoga sp. having higher perhydrolytic specific activity and/or improved selectivity for perhydrolysis when used to prepare peroxycarboxylic acid from carboxylic acid esters.
Although the CE-7 family of carbohydrate esterases has been identified as a class of perhydrolytic enzymes having desirable specific activities for peroxycarboxylic acid formation (e.g., peracetic acid formation; PAAF) and/or desirable perhydrolysis to hydrolysis (P/H) ratios for carboxylic acid ester substrates, these enzymes may also have an undesirable enzymatic activity for hydrolyzing the peroxycarboxylic acid product (e.g., peracetic acid hydrolysis; PAAH) to the corresponding carboxylic acid and hydrogen peroxide. As such, an enzyme catalyst comprising a CE-7 perhydrolase characterized by a higher PAAF/PAAH ratio may provide greater peroxycarboxylic acid stability in formulations comprising the enzyme catalyst.
The problem to be solved is to provide an enzyme catalyst comprising a CE-7 carbohydrate esterase having perhydrolytic activity and a higher PAAF/PAAH ratio of specific activities.